Better Boating

What is a Safe Speed for Boating in the Fog?

Face it; nobody likes running in the fog. The first time I was ever caught was in the early 80s. We were anchored overnight on Aquarius in Tarpaulin Cove with Peter and Mary Lee and we woke up to pea soup.

The only electronics onboard was a VHF radio with the Marine Weather Channel. The forecast called for fog all day. Our next stop was Vineyard Haven, so we headed out blind around 10:00 AM. Peter stood on the bow with an air horn, and we headed straight across Vineyard Sound until we nearly hit Martha’s Vineyard. Then we followed the shoreline east to Vineyard Haven.

My next encounter was about ten years ago, bringing Mean Kitty (Hydrasports 3300) over from Peases Point to Mattapoisett Town Pier for the end-of-season haul out.

Mean Kitty had traditional radar (not a chart-plotter overlay), so I didn’t even attempt to use it. I started using GPS at 5 knots, but my GPS didn’t refresh fast enough to show my heading at low speed accurately.

I quickly found myself driving in circles around the Point Connett moorings. I switched to compass, maps, sounding my fog horn, and picked my way around Anjelica Point’s rocks.

Fast Forward to 2016, and we’d upgraded to Tenacity (Back Cove Downeast 37) along with a thoroughly modern Garmin Electronics and HD Radar System. We were taking some friends to Sakonnet for lunch, and although the fog was lifting when left Mattapoisett, it re-emerged just north of Cuttyhunk.

I fired up the radar, switched to GPS Overlay, and plotted an offshore course three miles south of The Wild Cats to Rhode Island. Once I got oriented, I could see we were pretty much out there alone, and I took her up to planing speed.

Since that day, I’ve logged well over 100 hours running by instruments only in fog. Still, I wouldn’t say I like it, but I’m confident I can see everything around me on my radar and AIS with plenty of time to take evasive action.

Then a week ago, I read a story in Soundings Online that gave me pause. The article essentially said everyone should slow to a crawl in fog and run as though they didn’t have radar.

I am an active member of a Facebook page devoted to Buzzards Bay Boaters, so I posted the article there. I mentioned that I regularly cruise by instruments in the fog and asked what others do.

The post drew dozens of emotional responses, and most of them were highly critical of anyone who runs their boat at any speed when the fog rolls in.

Whenever I see that kind of reaction, I know I’m on to a good subject, so I decided to dig a little deeper and figure out what seasoned captains do when the fog rolls in.

I Sought Expert Help!

I know from experience that professional Captains do run at speed in the fog because I see them on AIS and radar when I’m out there. I also know that the island ferries run on time in the fog.

So how do they do it?

The first expert I contacted was my #1 electronics guy – Scott Keurtzberg, Owner SK Marine Electronics in New Bedford. Scott equips all size boats including mega yachts and ferries.

I also spoke to several professional sea captains I’ve met over the years. These are guys who deliver yachts up and down the east coast, run offshore fishing boats, and one is even a Sea Tow operator. Combined, they represented tens of thousands of hours of running in the fog.

I confirmed much of what I thought but certainly learned things I hadn’t considered. Given the heated reaction to the Facebook post, it’s clear that this is an important topic, so I decided to share what I learned about Safe Speed in the fog on My Buzzards Bay.

Safe Speed According to the US Coast Guard

The USCG’s Rules The Road define Safe Speed…

USCG Rule 6

There are a few significant takeaways from this rule:

  1. There is no hard and fast definition of Safe Speed. The Coast Guard leaves it up to each Captain’s judgment and specifies some of the factors a captain should consider.
  2. There are two sets of rules; one for all vessels and one just for vessels operating on the radar.
  3. The radar rules (b) highlight both the radar equipment and the judgement of the operator with the use of the word “possibility.”

The Coast Guard further discusses running in fog in Rule 19…

USCG Rule 19

The most interesting takeaway here is (d) in that it discusses the situation whereby a vessel detects another vessel “by radar alone.” This clearly contemplates running by instruments only as still being a Safe Speed.

The experts I spoke to confirmed this and broke down the running in fog equation as follows:

  1. What are the capabilities of the electronics and radar onboard?
  2. How well does the Captain know how to use the equipment’s capabilities onboard?
  3. Where are you operating – how congested is it and what’s the likelihood of small boats and/debris in the water?

I think the USCG’s Rule 6 and 19 essentially lay responsibility for answering each of these questions on each vessel’s Captain.

Let’s look at each one of these in more detail…

As mentioned earlier, I regularly see ferries and larger ships running at speed in the fog. This piqued my curiosity about their electronics and radar – what are they using for electronics?

What are the capabilities of your electronics and radar onboard?

Scott (SK Marine Electronics) confirmed that the island ferries are at best using the same electronics as those installed on Relentless. He also emphasized that every boat must proceed with caution in the fog – even a ferry.

Of course, ferries are huge, and while they can undoubtedly plow through anything, a collision would certainly do serious damage to the other boat and even kill someone – ending the career of the Captain or worse. So it’s doubtful that they’d travel at speed in the fog unless they believed it was completely safe.

Scott also pointed out that Navy Ships are designed to elude conventional radar. This made sense, so I did a little research and discovered that while this is generally true, Congress intervened in 2017, and since then, all Navy Ships in US Waters are required to have their AIS Transponders on at all times.

No matter what anyone tells you, running in fog is a calculated risk, and the decision of what’s a Safe Speed lies in the captain’s judgment.

1. Without radar, Safe Speed is clearly defined in Rule 6 – you simply cannot go faster than you can see – meaning far enough to stop short of a collision. We’ve all been in pea soup with less than 50’ of visibility. If you’re running without radar in pea soup at any speed, you are putting your boat and crew in peril.

2. Thinking of electronics as a ladder of sophistication, the first rung would be the kind of traditional radar that’s been around for decades.

As with all radar, the ability to “see” targets will be limited to the performance of the Radar Unit that sits on top of the boat; its size, speed, and wattage define the clarity of targets on the screen.

The biggest problem with this kind of old-school radar is that it’s not really practical for the Captain to monitor the screen while steering the boat. It requires an independent operator to track targets, look out for potential collisions and then alert the Captain when evasive action is required. Needless to say, this is fraught with risk if the target comes up too fast to react in time.

As an interesting side note, one Sea Tow Captain pointed out that their boat’s radar didn’t operate properly at low speed because the bow rise tilted the plane of the radar unit such that it was scanning the sky in front of him and the sea behind. He told me he traveled at planing speed in fog just to make his radar operate correctly.

3. The next ring on the ladder are integrated systems that overlay the radar tracking on top of a high-resolution chart-plotter. This is what we had on Tenacity, Vigilant, and now Relentless.

Radar overlays on the Chartplotter make it much easier to pick up risky targets by highlighting buoys and shorelines that are supposed to be there – making it very easy to spot unknown blips and track them as they are likely other boats.

4. An autopilot removes the need for an independent radar operator and allows the Captain to focus on the screen with one hand on the throttles. Others onboard should continue to operate as lookouts.

5. Relentless has a Garmin Fantom 4 that was manufactured in 2017. Garmin no longer sells this unit but does provide quarterly updates. While I’m sure that their current models are even more impressive, this exercise got me to open the operators manual to understand our capabilities better and what I learned blew me away.

Quite frankly, I had no idea that these options existed, but now that I know, I plan to take a deeper dive once I get back aboard.

6. Adding AIS provides not just visibility but also the speed and heading of other boats in the area. All big boats, commercial boats, and fishing boats over 15 meters must have AIS.

Here’s a link to a nice piece describing AIS.

7. The Fantom 4 also provides ARPA and MARPA capability. These functions essentially allow operators to “tag” a blip on the radar and quickly identify its heading. Once the heading is calculated, you can quickly identify the risk of collision.

8. Systems like our Garmin Fantom allows one to set up a Safe Zone that will track the bearing and speed of every AIS, ARPA, or MARPA target in the area sound an alarm if a risk of collision arises.

How well do you know how to use the capabilities of your equipment onboard?

Although I know how to basically operate my electronics onboard, I’m not sure I’m an expert. If this exercise has taught me anything, it’s that I need to learn a lot more about operating my radar.

Everyone I spoke to suggested running radar at all times – even on a clear day. The reason is simple; it will enable us to get a feel for the difference between seeing a blip on the radar and seeing it with our own two eyes.

I also think it’s a great way to troubleshoot my specific system by making sure everything I see with my eyes is showing up as a blip on the screen.

By the way, it’s also the law – USCG Rule 7…

If you’re running on a clear day without your radar on, you are violating Rule 7.

SK set up my Garmin system and showed me how to use it, but two Captains suggested that I reset it to the original factory settings and learn to set it up from scratch. Another suggested toggling between different ranges, gains, and modes on a clear day to see how the screen blips change.

The logic is simple. If you want to safely run at speed in the fog, you must be able to replace your eyes and ears with radar. And to do this takes practice, practice, practice!

Where are you operating; how congested is it and what’s the likelihood of small boats and/debris in the water?

The Captains I spoke to said that they let the nature of the traffic around them and congestion drive their Safe Speed. Specifically, even the most sophisticated electronics can fail to pick a person sitting in a rowboat, a partially submerged log, debris, lobster pots, or a sea turtle.

That said, partially submerged objects are often invisible, even on a clear day. My friend Captain Tom hit something in Vineyard Sound on a clear day that bent his prop. He never found out what it was, but it was likely a sea turtle.

Fortunately, in New England, we don’t have much risk of floating logs or debris, especially well offshore (this in not true in the Northwest or down south.)

As mentioned earlier, this is why I operate as if I had no radar near shore or in congested areas. The critical question is “under what conditions is it safe to accelerate to planing speed?”

The experts I spoke to agreed that about 3 miles offshore was the threshold for running by instruments. Most boats this far out on a foggy day have AIS, and all are large enough to spot on radar.

In my thousands of hours running offshore to and from Block Island and Nantucket, I can confidently say that I’ve never seen a boat that would not show up on radar 3 miles offshore.

This is where I pick up speed if I have a lot of ground to cover. Understand, I only pick speed when my screen is clear of unknown blips.

I like to monitor a two-mile circular zone around me, and I immediately change course to steer clear of any boat that enters that zone. And, of course, I slow down and sound my horn if another boat gets uncomfortably close.

The Preferred Option – Avoid Fog If Possible

All but one Captain agreed that they’d stay put onshore when fog hits if they had the option. I agree, but if my trip is largely offshore and/or the forecast calls for the fog to lift, I may depart in one-mile visibility and roll with the punches.

This has been an eye-opening exercise for me, and while I’m confident that I never ran in fog at an Unsafe Speed, I have learned a lot that will help me operate more confidently in the future.

Categories: Better Boating

2 replies »

  1. This is awesome useful information Dave I learned a lot thank you for the education and enlightenment. I’m going to take a stab and guess the majority of the naysayers were quite possibly Biden voters lol not to throw a political twist to this but just an observation and thought it was worth mentioning especially in light of the current shit show we are are all unfortunately enduring.
    In all honesty I myself would not be comfortable running at 30 knots in limited visibility, That is your absolute right unfortunately there are a good portion of blowhards and want to be boaters on Facebook and the BB site you’re clearly not one of them and have a god given right to do what ever you are comfortable with. God bless & help AMERICA!!


    • Thanks John,

      I recently got my License to Carry and the instructor told us that the proper way to carry a pistol was inside your belt, just below the belly button, with the safety OFF. He then asked the class “Why?”

      The answer was “Unless you’re confident enough in your firearm skills to carry like that and not worry about shooting yourself in the balls, DO NOT CARRY A WEAPON.”

      I think running at speed in the fog is the same thing – unless you fully trust your equipment and knowledge, STAY HOME.

      If you can guess the political affiliation of trolls based on their comments, you’re a better man than me. My guess is they had weak electronics and operating skills, smaller boats, and seldom run five miles offshore.

      In terms of speed, my original post said 30 MPH (not knots), but that was a bit of an exaggeration. I’m really seeking efficient planing speed which is 22-25 knots on my boat or 0.75 MPG.

      As you probably know, a fog bank is often followed by wind and waves, so if I’m 50-60 miles offshore, I want to get home ahead of the wind.


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